hello this is an introductory course on circuits and systems or networks and systems
suitable for an under graduated students major in electrical engineering with either to power
or communication option in this course we will study the dynamic
behavior of systems and networks you will be expose to a
variety of tools and techniques which are used to study the behavior of the systems
under with the dynamic inputs so that you can gain an or what particular
techniques to choose under a given situation when talking about systems we should also
talk about signals the input variables to a system the response
variable that where looking for and the various intermediate variables which occur a different
points in the system are all collectively called signals
and this is the term which we will use to describe this
variables associated with systems later on we will say that a network is a special kind
of systems and the voltage and current variables associate
with a circuit or a network therefore are also called signals
in the particular contest of a electrical work these signals are usually functions of
time a study of the characteristic of the signals and there
analysis therefore it an integral component of our course
as a matter of fact it is the interplay between the signals and systems that will be the main
theme or and focus of our course among the topics which
will study or for your methods for your transform laplace transform method network functions
and network theorems z transform methods and state variable
techniques these will be the various topics that will be broadly covered under this course
we shall for the most part confine ourselves largely
to the discussion of linear time invariant systems the
meaning of these 2 adjectives linear and time invariant will become clear as we go along
suppose is to say that the form a large class of useful systems so at
the end of this course you will have with you a tool kit of available
techniques so that you can choose 1of these took techniques for the solution of with a
dynamic behavior of a network and system belonging to this very
large class of linear time invariant systems before a proceed
before we proceed further to discuss the meaning of a system let me first talk about the various
text books and reference books that we may like to refer
to during the your study of the material under this course
you may use this book to have some of your doubts clarify to deepened your understanding
of a particular topic may be to get additional information
related to some of the topics that are discussed here but most
importantly you should this book for working out the various problems and answering the
various questions that are given as exercises in this book particularly
for a subject with an analytic analytic orientation like network and systems it is very important
that you should work out a large number of this quantitative problems and answer this
various questions it is only through such exercises that you
can from your understanding with the subject make your grip
of the various techniques stronger and another important aspect with this is that like an
any other discipline in network and systems also there
will be always a number of approaches to solve a
particular problem only through working out to this various exercises you will be having
the ability to choose a the most direct method of attack
for any 1problem you have necessary expertise to gain the
insight so that you can select the most appropriate method of attack for the solution of a problem
and not only that to carry out the solution correctly
and in quick time so i would once again emphasize the importance of working out a variety of
problems and you can use some of the text books which
i am going to mention right now ah as a source material for this problems now the
particular text books that i would like to recommend are hayt and kemmerly engineering
circuit and analysis van valkenburg network analysis
these 2are very popular books in this field openheim willksy and young signals and systems
is a very comprehensive gives a very comprehensive coverage of the topic that are covered in
this course that’s an additional topics and this also
contains a wealth of problems and exercises in addition to these 3 books you
have a book by cheng titled analysis of linear systems liu and liu linear systems analysis
and a sixth book by aatre network theory and filter
design it contains discussion of some other topics we are going to cover in this course
like state variable methods and so on which are
not perhaps found in some of the other books by way of a background i expect of you to
follow this course let me mention that ah i expect
the students to have a background on the following topics i assumed that you had a basic course
in electrical circuit analysis which includes the discussion of the properties
of various circuits elements dc and ac circuits analysis ac circuit analysis on the study
state sinusoidal conditions and an idea of elementary
transients time constants and rc circuit rl circuit and so on and setting up the differential
equation pertaining to simple circuits this is a background in electrical engineering
that 1you have as per mathematics systems and you should
be familiar with elements of differential and integral calculus solution of simple linear
differential equations ordinary differential equations a constant coefficient you should
also have an idea of matrices and determinants solution of linear algebraic equations and
then elements of complex variable theory is also
expected a few to follow this course so this is the background what 1would expect you to
have follow this course now let us discuss what
a system means all of us have an idea what a
system is constituted of through its usage in every day terminology we may formally say
a system is a collection of components put together
to serve a particular purpose these components are
are system components that are unified through some kind of int inter dependence among
them they react with each other so that the whole system function as a whole to serve
a particular purpose you may think of a power system the
national educational system hospital systems railway
systems transportation systems and so on and so forth many of these systems also have as
a integral component the interaction of people for example
in social economic system all these are constituents of systems now therefore a system is a collection
of objects united through some form of interdependence among the various components or sub systems
as you may call now the variables that describe the status of
this various components and a system may be quite diverse depending upon the nature of
the component the nature of the system and so and so forth for
example if you are talking about an electro mechanical
system you may have the electrical variables voltage and current associate with a electrical
components and mechanical variables like force and velocity
which describe the status of the mechanical components
at the particular point of in the system at a particular point in the system therefore
system is a_ concept which includes the whole variety of
ah situations that once comes across now what about a network
literally speaking a network is a structure which resembles a kind of net but in our particular
contest the term network to describe a system in which
all the components are of a related kind that means the
variables which are of importance in this system are all of the same kind so in a particular
electrical network for example is a special kind of a
system in which the variables are voltages and currents most
often that is these are the 2variables which are the interest towards the electrical network
similarly we can have a network representing a mechanical
system which will call a mechanical network we use the
variables may be velocities and then force and so on and so forth so we can think of
a net network as a special kind of a system in electrical network
in particular is what constitutes the focus of our
discussion here now we analyzing these systems and networks the first up usually is to model
the system in terms of idealized components put together
in a particular fashion this evolution of the model is
d1with 2conflicting requirements in our mind what are the 2conflicting requirements first
of all we should like to have the model as realistic
as possible so that it stimulates the real system in other
words we should like to make the model as complex as possible so that we loose as little
information about the system as possible on the other
hand we should also like to make the model as simple as possible
to lend itself to convenient mathematical analysis so that the person uses this model
for analysis and synthesis we retain a sanity in a sense because
if it is going to be a huge a complex type of model
we will be never to able solve it therefore these are the 2conflicting requirements in
the evolution of a model of a given physical system the on
1hand it should be as complex as possible so that it will
loose as little information about the system as possible at the same time it has got to
be simple enough to be lend itself to convenient mathematical
analysis now we are very often refer to the model itself
as a system even though we must always keep at the back of our mind that the model is
a mathematical representation is an idealized representation
the physi the actual physical system is something different
and some in some ways a physical system may not the characteristic may not agree with
a model and if it so then we have to the find the model to make
it more realistic where ever it is warranted now in arri
in arriving at a model for a particular system the derivation of the model is specific to
the particular discipline you must study the situation you
must know the characteristic of these and arrive a
suitable model but once we have evolved a model then a whole lot of the system can be
analyses through a common frame work a common set of mathematical
tools which can be used to analyze a whole lot of this
different system system models because the mathematical equations that govern the operation
of the various system are more or less the same therefore
there is a unifying body of techniques and knowledge which
come under the general title system theory at principle of the system analysis which
will be the main scope of our study in under this course
